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Using stacking of images obtained at different epochs, we studied the variability properties of linear polarization of active galactic nucleus (AGN) jets on parsec-scales. Our sample is drawn from the MOJAVE programme, and consists of 436 AGNs manifesting core-jet morphology and having at least five VLBA observing epochs at 15 GHz from 1996 January through 2019 August, with some additional archival VLBA data reduced by us. We employed a stacking procedure and constructed maps of (i) standard deviation of fractional polarization and electric vector position angle (EVPA) over epochs as the measure of variability and (ii) median polarization degree to quantify typical values in time. The distributions of these values along and across the jet were analysed for the whole sample for the first time. We found that core EVPA variability is typically higher than that of the jet, presumably due to component blending and outflow bends in the core. The BL Lacertae object cores have lower EVPA variability, compared to that of quasars, possibly due to lower Faraday rotation measure, suggesting a stronger ordered magnetic field component. The EVPA becomes more stable down the jet. Most of the sources showing this trend have a time coverage of more than 12 yr and at least 15 epochs. The possible cause could be the increase of stability in the magnetic field direction, reflecting an increase in the fraction of the magnetic field that is ordered. There are no significant optical-class-dependent or spectral-class-dependent relations in the EVPA variability properties in AGN jets. [ABSTRACT FROM AUTHOR]

We analysed the parsec-scale linear polarization properties of 436 active galactic nuclei (AGNs) based on 15 GHz polarimetric Very Long Baseline Array observations. We present polarization and total intensity images averaged over at least five epochs since 1996 January 19 through 2019 August 4. Stacking improves the image sensitivity down to ∼30 μJy beam−1 and effectively fills out the jet cross-section both in total intensity and linear polarization. It delineates the long-term persistent magnetic field configuration and its regularity by restoring spatial distributions of the electric vector position angle (EVPA) and fractional polarization, respectively. On average, about 10 yr of stacking period is needed to reveal the stable and most-complete polarization distribution of a source. We find that the degree of polarization significantly increases down and across the jet towards its edges, typically manifesting U or W-shaped transverse profiles, suggesting a presence of a large-scale helical magnetic field associated with the outflow. In some AGN jets, mainly BL Lacs, we detect quasi-constant fractional polarization profiles across the jet, accompanied by EVPAs that closely follow the outflow. BL Lacs show higher fractional polarization values in their cores and jets than those in quasars up to hectoparsec de-projected scales, while on larger scales, they become comparable. High-synchrotron-peaked BL Lac jets are found to be less polarized than intermediate and low-synchrotron-peaked BL Lacs. The spatial distribution of the EVPAs in BL Lacs tend to align with the local jet direction, while quasars show an excess of orthogonal polarization orientation. [ABSTRACT FROM AUTHOR]

On 2019/07/30.86853 ut , IceCube detected a high-energy astrophysical neutrino candidate. The Flat Spectrum Radio Quasar PKS 1502+106 is located within the 50 per cent uncertainty region of the event. Our analysis of 15 GHz Very Long Baseline Array (VLBA) and astrometric 8 GHz VLBA data, in a time span prior and after the IceCube event, reveals evidence for a radio ring structure that develops with time. Several arc-structures evolve perpendicular to the jet ridge line. We find evidence for precession of a curved jet based on kinematic modelling and a periodicity analysis. An outflowing broad line region (BLR) based on the C  iv line emission (Sloan Digital Sky Survey) is found. We attribute the atypical ring to an interaction of the precessing jet with the outflowing material. We discuss our findings in the context of a spine-sheath scenario where the ring reveals the sheath and its interaction with the surroundings (narrow line region, NLR, clouds). We find that the radio emission is correlated with the γ-ray emission, with radio lagging the γ-rays. Based on the γ-ray variability time-scale, we constrain the γ-ray emission zone to the BLR (30–200  r g) and within the jet launching region. We discuss that the outflowing BLR provides the external radiation field for γ-ray production via external Compton scattering. The neutrino is most likely produced by proton–proton interaction in the blazar zone (beyond the BLR), enabled by episodic encounters of the jet with dense clouds, i.e. some molecular cloud in the NLR. [ABSTRACT FROM AUTHOR]

We report the results of decade-long (2008–2018) γ-ray to 1 GHz radio monitoring of the blazar 3C 279, including GASP/WEBT, Fermi and Swift data, as well as polarimetric and spectroscopic data. The X-ray and γ-ray light curves correlate well, with no delay |$\gtrsim 3$| h, implying general cospatiality of the emission regions. The γ-ray–optical flux–flux relation changes with activity state, ranging from a linear to a more complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz Very Long Baseline Array images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. Apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk Lorentz factors close to those needed to explain γ-ray variability on very short time-scales. The Mg  ii emission line flux in the 'blue' and 'red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse Compton scattering. In the radio bands, we find progressive delays of the most prominent light-curve maxima with decreasing frequency, as expected from the frequency dependence of the τ = 1 surface of synchrotron self-absorption. The global maximum in the 86 GHz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at ∼5 GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet. [ABSTRACT FROM AUTHOR]

Synchrotron self-absorption in active galactic nuclei (AGN) jets manifests itself as a time delay between flares observed at high and low radio frequencies. It is also responsible for the observing frequency-dependent change in size and position of the apparent base of the jet, aka the core shift effect, detected with very long baseline interferometry (VLBI). We measure the time delays and the core shifts in 11 radio-loud AGN to estimate the speed of their jets without relying on multi-epoch VLBI kinematics analysis. The 15–8 GHz total flux density time lags are obtained using Gaussian process regression, the core shift values are measured using VLBI observations and adopted from the literature. A strong correlation is found between the apparent core shift and the observed time delay. Our estimate of the jet speed is higher than the apparent speed of the fastest VLBI components by the median coefficient of 1.4. The coefficient ranges for individual sources from 0.5 to 20. We derive Doppler factors, Lorentz factors, and viewing angles of the jets, as well as the corresponding de-projected distance from the jet base to the core. The results support evidence for acceleration of the jets with bulk motion Lorentz factor Γ ∝  R 0.52±0.03 on de-projected scales R of 0.5–500 parsecs. [ABSTRACT FROM AUTHOR]

We present the results of a detailed X-ray timing and spectral analysis of the BL Lacertae source OJ 287 with X-ray telescope (XRT) onboard Neil Gehrels Swift Observatory, focused on the period of its significantly enhanced X-ray flaring activity during 2016 October–2017 April. In this epoch, the 0.3–10 keV count rate from the XRT observations showed an increase by a factor of ∼10 compared to the quiescent level observed in 2016 April–May, and the mean X-ray flux was a factor of 4.5 higher than in previous years. The source underwent high X-ray flaring activity on weekly time-scales and showed 32 instances of 0.3–10 keV intraday variability (detected within the exposures shorter than 1 ks in the majority of cases) with fractional variability amplitudes of 7–60 per cent. Most of the 0.3–10 keV spectra spectra fitted well with a simple power law, yielding a wide range of the 0.3–10 keV photon index Γ = 1.90–2.90. We found 29 spectra showing an upward curvature due to the significant contribution made by the X-ray photons of inverse Compton origin. The spectral variability of OJ 287 was characterized by the dominance of a 'softer-when-brighter' spectral trend, explained by the emergence of a new soft component during X-ray flares. Similar to X-rays, the source underwent a strong outburst by factors of 4.6–6.5 in the optical–ultraviolet energy range which showed a positive correlation with the X-ray emission, indicating its origin to be related to the same electron population, predominantly via the synchrotron mechanism. [ABSTRACT FROM AUTHOR]

OJ287 is the best candidate active galactic nucleus (AGN) for hosting a supermassive binary black hole (SMBBH) at very close separation. We present 120 Very Long Baseline Array (VLBA) observations (at 15 GHz) covering the time between April 1995 and April 2017. We find that the OJ287 radio jet is precessing on a time-scale of ∼22 yr. In addition, our data are consistent with a jet-axis rotation on a yearly time-scale. We model the precession (24 ± 2 yr) and combined motion of jet precession and jet-axis rotation. The jet motion explains the variability of the total radio flux-density via viewing angle changes and Doppler beaming. Half of the jet-precession time-scale is of the order of the dominant optical periodicity time-scale. We suggest that the optical emission is synchrotron emission and related to the jet radiation. The jet dynamics and flux-density light curves can be understood in terms of geometrical effects. Disturbances of an accretion disc caused by a plunging BH do not seem necessary to explain the observed variability. Although the SMBBH model does not seem necessary to explain the observed variability, an SMBBH or Lense-Thirring precession (disc around single BH) seem to be required to explain the time-scale of the precessing motion. Besides jet rotation also nutation of the jet axis could explain the observed motion of the jet axis. We find a strikingly similar scaling for the time-scales for precession and nutation as indicated for SS433 with a factor of roughly 50 times longer in OJ287. [ABSTRACT FROM AUTHOR]

Clues to the physical conditions in radio cores of blazars come from measurements of brightness temperatures as well as effects produced by intrinsic opacity. We study the properties of the ultra-compact blazar AO0235+164 with RadioAstron ground-space radio interferometer, multifrequency VLBA, EVN, and single-dish radio observations. We employ visibility modelling and image stacking for deriving structure and kinematics of the source, and use Gaussian process regression to find the relative multiband time delays of the flares. The multifrequency core size and time lags support prevailing synchrotron self-absorption. The intrinsic brightness temperature of the core derived from ground-based very long baseline interferometry (VLBI) is close to the equipartition regime value. In the same time, there is evidence for ultra-compact features of the size of less than 10 μas in the source, which might be responsible for the extreme apparent brightness temperatures of up to 1014 K as measured by RadioAstron. In 2007-2016 the VLBI components in the source at 43 GHz are found predominantly in two directions, suggesting a bend of the outflow from southern to northern direction. The apparent opening angle of the jet seen in the stacked image at 43 GHz is two times wider than that at 15 GHz, indicating a collimation of the flow within the central 1.5 mas. We estimate the Lorentz factor Γ = 14, the Doppler factor δ = 21, and the viewing angle θ = 1.7° of the apparent jet base, derive the gradients of magnetic field strength and electron density in the outflow, and the distance between jet apex and the core at each frequency. [ABSTRACT FROM AUTHOR]

The X-ray variability of the BL Lacertae source 1ES 1959+650 was studied intensively with X-ray telescope (XRT) onboard Swift during 2016 January-August. In this paper, we present the results obtained during this campaign. A long-term high X-ray state was superimposed by shorter-term flares by a factor of 1.9-4.7.We found 35 instances of intra-day variability which showed very fast flux changes by 14-21 per cent occurring within 1 ks and a decline by a factor of 2.3 in 17.2 ks. Similarly to the previous years, this period sometimes was characterized by a lack of correlated X-ray and TeV variability, indicating that the high-energy emission in 1ES 1959+650 was generated in the emission region more complex than a single zone. The source showed a significant X-ray - high-energy flux correlation, while the former was not correlated with the optical-UV fluxes. The best fits of the 0.3-10 keV spectra were mainly obtained using the log-parabola model. Strong spectral variability was detected, shifting the peak of the spectral energy distribution by more than 10 keV that happens rarely in blazars. During some strong short-term flares, the photon index at 1 keV frequently became harder than 1.70, and the spectral evolution was characterized by a harder-when-brighter behaviour. [ABSTRACT FROM AUTHOR]

The blazar 3C 454.3 exhibited a strong flare seen in γ-rays, X-rays and optical/near-infrared bands during 2009 December 3-12. Emission in the V and J bands rose more gradually than did the γ-rays and soft X-rays, though all peaked at nearly the same time. Optical polarization measurements showed dramatic changes during the flare, with a strong anticorrelation between optical flux and degree of polarization (which rose from ~3 to ~20 per cent) during the declining phase of the flare. The flare was accompanied by large rapid swings in polarization angle of ~170°. This combination of behaviours appears to be unique. We have cm-band radio data during the same period but they show no correlation with variations at higher frequencies. Such peculiar behaviour may be explained using jet models incorporating fully relativistic effects with a dominant source region moving along a helical path or by a shock-in-jet model incorporating three-dimensional radiation transfer if there is a dominant helical magnetic field. We find that spectral energy distributions at different times during the flare can be fit using modified one-zone models where only the magnetic field strength and particle break frequencies and normalizations need change. An optical spectrum taken at nearly the same time provides an estimate for the central black hole mass of ~2.3 × 109M☉.We also consider two weaker flares seen during the ~200 d span over which multiband data are available. In one of them, the V and J bands appear to lead the γ-ray and X-ray bands by a few days; in the other, all variations are simultaneous. [ABSTRACT FROM AUTHOR]

We studied the pc-scale core shift effect using radio light curves for three blazars, S5 0716+714, 3C 279 and BL Lacertae, which were monitored at five frequencies (ν) between 4.8 and 36.8 GHz using the University of Michigan Radio Astronomical Observatory (UMRAO), the Crimean Astrophysical Observatory (CrAO) and Mets¨ahovi Radio Observatory for over 40 yr. Flares were Gaussian fitted to derive time delays between observed frequencies for each flare (Δt), peak amplitude (A) and their half width. Using A∝να, we infer α in the range of −16.67–2.41 and using Δt ∝ ν1/kr , we infer kr ∼ 1, employed in the context of equipartition between magnetic and kinetic energy density for parameter estimation. From the estimated core position offset (λrν ) and the core radius (rcore), we infer that opacity model may not be valid in all cases. The mean magnetic field strengths at 1 pc (B1) and at the core (Bcore) are in agreement with previous estimates. We apply the magnetically arrested disc model to estimate black hole spins in the range of 0.15–0.9 for these blazars, indicating that the model is consistent with expected accretion mode in such sources. The power-law–shaped power spectral density has slopes −1.3 to −2.3 and is interpreted in terms of multiple shocks or magnetic instabilities. [ABSTRACT FROM AUTHOR]

Despite the fragmentation of healthcare provision being considered one of the main obstacles to attaining effective health care in Latin America, very little is known about patients' perceptions. This paper analyses the level of continuity of health care perceived by users and explores influencing factors in two municipalities of Colombia and Brazil, by means of a cross-sectional study based on a survey of a multistage probability sample of people who had suffered at least one health problem within the previous three months (2163 in Colombia; 2167 in Brazil). An adapted and validated version of the CCAENA© (Questionnaire of care continuity across levels of health care) was applied. Logistic regression models were generated to assess the relationship between perceptions of the different types of health care continuity and sociodemographic characteristics, health needs, and organizational factors. The results show lower levels of continuity across care levels in information transfer and care coherence and higher levels for the ongoing patient-doctor relationship, albeit with differences between the two countries. They also show greater consistency of doctors in the Brazilian study areas, especially in primary care. Consistency of doctors was not only positively associated with the patient-doctor ongoing relationship in the study areas of both countries, but also with information transfer and care coherence across care levels. The study area and health needs (the latter negatively for patients with poor self-rated health and positively for those with at least one chronic condition) were associated with all types of continuity of care. The influence of the sex or income varied depending on the country. The influence of the insurance scheme in the Colombian sample was not statistically significant. Both countries should implement policies to improve coordination between care levels, especially regarding information transfer and job stability for primary care doctors, both key factors to guarantee quality of care. [ABSTRACT FROM AUTHOR]

We consider the high radio-frequency (15-353 GHz) properties and variability of 35 brightest cluster galaxies (BCGs). These are the most core-dominated sources drawn from a parent sample of more than 700 X-ray selected clusters, thus allowing us to relate our results to the general population. We find that =6.0 per cent of our parent sample (=15.1 per cent if only cool-core clusters are considered) contain a radio source at 150 GHz of at least 3 mJy (1×1023 W Hz-1 at our median redshift of z 0.13). Furthermore, =3.4 per cent of the BCGs in our parent sample contain a peaked component (Gigahertz Peaked Spectrum, GPS) in their spectra that peaks above 2 GHz, increasing to =8.5 per cent if only cool-core clusters are considered. We see little evidence for strong variability at 15 GHz on short (week-month) time-scales although we see variations greater than 20 per cent at 150 GHz over six-month time frames for 4 of the 23 sources with multi-epoch observations. Much more prevalent is long-term (year-decade time-scale) variability, with average annual amplitude variations greater than 1 per cent at 15 GHz being commonplace. There is a weak trend towards higher variability as the peak of the GPS-like component occurs at higher frequency. We demonstrate the complexity that is seen in the radio spectra of BCGs and discuss the potentially significant implications of these high-peaking components for Sunyaev-Zel'dovich cluster searches. [ABSTRACT FROM AUTHOR]

We study the core shift effect in the parsec-scale jet of the blazar 3C 454.3 using the 4.8–36.8 GHz radio light curves obtained from three decades of continuous monitoring. From a piecewise Gaussian fit to each flare, time lags Δt between the observation frequencies ν and spectral indices α based on peak amplitudes A are determined. From the fit Δt ∝ ν1/kr, kr = 1.10 ± 0.18 indicating equipartition between the magnetic field energy density and the particle energy density. From the fit A ∝ να, α is in the range −0.24 to 1.52. A mean magnetic field strength at 1 pc, B1 = 0.5 ± 0.2 G, and at the core, Bcore = 46 ± 16 mG, are inferred, consistent with previous estimates. The measure of core position offset is Ωrν = 6.4 ± 2.8 pc GHz1/kr when averaged over all frequency pairs. Based on the statistical trend shown by the measured core radius fcore as a function of ν, we infer that the synchrotron opacity model may not be valid for all cases. A Fourier periodogram analysis yields power-law slopes in the range −1.6 to −3.5 describing the power spectral density shape and gives bend time-scales in the range 0.52–0.66 yr. This result, and both positive and negative α, indicate that the flares originate from multiple shocks in a small region. Important objectives met in our study include: the demonstration of the computational efficiency and statistical basis of the piecewise Gaussian fit; consistency with previously reported results; evidence for the core shift dependence on observation frequency and its utility in jet diagnostics in the region close to the resolving limit of very long baseline interferometry observations. [ABSTRACT FROM AUTHOR]

PKS 0521-36 is an active galactic nucleus (AGN) with uncertain classification. We investigate the properties of this source from radio to γ-rays. The broad emission lines in the optical and ultraviolet bands and steep radio spectrum indicate a possible classification as an intermediate object between broad-line radio galaxies (BLRG) and steep spectrum radio quasars (SSRQ). On pc-scales PKS 0521-36 shows a knotty structure similar to misaligned AGN. The core dominance and the γ-ray properties are similar to those estimated for other SSRQ and BLRG detected in γ-rays, suggesting an intermediate viewing angle with respect to the observer. In this context the flaring activity detected from this source by Fermi-Large Area Telescope between 2010 June and 2012 February is very intriguing. We discuss the γ-ray emission of this source in the framework of the structured jet scenario, comparing the spectral energy distribution (SED) of the flaring state in 2010 June with that of a low state. We present three alternative models corresponding to three different choices of the viewing angles θv = 6°, 15°, and 20°. We obtain a good fit for the first two cases, but the SED obtained with θv = 15° if observed at a small angle does not resemble that of a typical blazar since the synchrotron emission should dominate by a large factor (γ100) the inverse Compton component. This suggests that a viewing angle between 6° and 15° is preferred, with the rapid variability observed during γ-ray flares favouring a smaller angle. However, we cannot rule out that PKS 0521-36 is the misaligned counterpart of a synchrotron-dominated blazar. [ABSTRACT FROM AUTHOR]

BSTRACT We discuss the opacity in the core regions of active galactic nuclei observed with Very Long Baseline Interferometry (VLBI), and describe a new method for deriving the frequency-dependent shifts of the VLBI core from the frequency-dependent time lags of flares observed with single-dish observations. Application of the method to the core shifts of the quasar 3C 345 shows a very good agreement between the core shifts directly measured from VLBI observations and derived from flares in the total flux density using the proposed method. The frequency-dependent time lags of flares can be used to derive physical parameters of the jets, such as distance from the VLBI core to the base of the jet and the magnetic fields in the core region. Our estimates for 3C 345 indicate core magnetic fields ≃0.1 G and magnetic field at 1 pc ≃ 0.4 G. [ABSTRACT FROM AUTHOR]

We investigate the (large-scale) bar fraction in a mass-complete sample of disc galaxies at in the Cosmological Evolution Survey (COSMOS) field. The fraction of barred discs strongly depends on mass, disc morphology and specific star formation rate (SSFR). At intermediate stellar mass the bar fraction in early-type discs is much higher, at all redshifts, by a factor of ∼2, than that in late-type discs. This trend is reversed at higher stellar mass , where the fraction of bars in early-type discs becomes significantly lower, at all redshifts, than that in late-type discs. The bar fractions for galaxies with low and high SSFRs closely follow those of the morphologically selected early- and late-type populations, respectively. This indicates a close correspondence between morphology and SSFR in disc galaxies at these earlier epochs. Interestingly, the total bar fraction in discs is built up by a factor of ∼2 over the redshift interval explored, while for discs it remains roughly constant. This indicates that, already by , spectral and morphological transformations in the most massive disc galaxies have largely converged to the familiar Hubble sequence that we observe in the local Universe, while for intermediate-mass discs this convergence is ongoing until at least . Moreover, these results highlight the importance of employing mass-limited samples for quantifying the evolution of barred galaxies. Finally, the evolution of the barred galaxy populations investigated does not depend on the large-scale environmental density (at least, on the scales which can be probed with the available photometric redshifts). [ABSTRACT FROM AUTHOR]

We present the result of our extensive intranight optical monitoring of the well-known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of R-band monitoring for a minimum duration of ∼4 hours, on 17 nights spanning 11 years (1998–2008). Using the CCD as an N-star photometer, a detection limit of around 1 per cent was attained for the intranight optical variability (INOV). Remarkably, an INOV amplitude of on hour-like time-scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of hours duration is known to be high . Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties. [ABSTRACT FROM AUTHOR]

We analyse the radio light curves of the blazars 1308+326, 2223−052 and 2251+158 using University of Michigan Radio Observatory and Metsähovi Radio Observatory multifrequency monitoring data combined with high-resolution very long baseline interferometry (VLBI) observations in order to extract the properties of prominent outbursts. The outbursts are classified as ‘core’ and ‘jet’ events according to their behaviour at different frequencies and their associations with features appearing in the VLBI jet. We define the activity cycle for each blazar as the time interval between successive ‘core’ outbursts. The durations of the activity cycle derived in this way are ≥14 yr for 1308+326, ∼12 yr for 2223−052 and 12.4 ± 0.6 yr for 2251+158. We find an unusual frequency dependence for the time profiles for a major flare in 1308+326, which may provide evidence for acceleration or bending of the jet flow in the optically thick part of the emission region. Analysis of these activity cycles, combined with our earlier results, leads us to suggest that more luminous blazars possess shorter activity cycles, consistent with the accretion rates being higher in more powerful sources (relative to the Eddington rate). [ABSTRACT FROM AUTHOR]

The combined data of the University of Michigan Radio Astronomy Observatory and Metsähovi Radio Observatory provide us with radio light curves for active galactic nuclei monitored by both observatories from 4.8 to 37 GHz covering time-intervals up to ∼25 yr. We consider here such composite light curves for four gamma-ray blazars that have been nearly continuously monitored at both observatories: 0458−020, 0528+134, 1730−130 and 2230+114. We have decomposed the most prominent outbursts in the light curves of these four blazars into individual components using Gaussian model fitting, and estimated the epochs, amplitudes, and half-widths of these components as functions of frequency. We attempt to distinguish ‘core outbursts’, which show frequency-dependent time-delays and are associated with brightening of the core, from ‘jet outbursts’, which appear nearly synchronous at all frequencies and are accompanied by the emergence of new jet components and their subsequent evolution. The outbursts in 0528+134 and 2230+114 display fine structure and consist of individual suboutbursts. Available 43-GHz Very Long Baseline Array images allow us to identify only one pure core outburst (in 2230+114) and one pure jet outburst (0458−020). Most of the outbursts analysed are mixed, in the sense that they display frequency-dependent time-delays (i.e. they are optically thick) and are associated with the eventual emergence of new jet components. The maxima of the jet and mixed outbursts probably correspond to epochs when newly ejected components become fully optically thin. These epochs are also marked by a significant increase in the angular velocities of the ejected components. There is evidence that the outbursts in 2230+114 repeat every , with the positions of individual suboutbursts being preserved from one quasi-periodic eight-year cycle to another, even though their amplitudes vary by more than a factor of 2. Preliminary estimates of the total durations of possible activity cycles based on an analysis of total flux-density variations and all available very long baseline interferometry data are given for the remaining sources. [ABSTRACT FROM AUTHOR]

Abstract The X-ray-bright Seyfert 1 galaxy III Zw 2 was observed with XMM–Newton in 2000 July. Its X-ray spectrum can be described by a power law of photon index Γ= 1.7 and an extremely broad (FWHM∼ 140 000 km s[sup -1] ) Fe Kα line at 6.44 keV. The iron line has an equivalent width of ∼800 eV. To study the long-term X-ray behaviour of the source we have analysed 25 yr of data, from 1975 to 2000. There is no evidence of significant intrinsic absorption within the source or of a soft X-ray excess in the XMM or archival data. We do not detect rapid X-ray variability (a few × 10[sup 3] s ) during any of the individual observations; however, on longer time-scales (a few years) the X-ray light curve shows 10-fold flux variations. We infer a black hole mass of ∼10[sup 9] M[sub ⊙] (from Hβ FWHM) for III Zw 2 which is much higher than some previous estimates. A comparison of X-ray variability with light curves at other wavelengths over a 25-yr period reveals correlated flux variations from radio to X-ray wavelengths. We interpret the variable radio to optical emission as synchrotron radiation, self-absorbed in the radio/millimetre region, and the X-rays mainly as a result of Compton up-scattering of low-energy photons by the population of high-energy electrons that give rise to the synchrotron radiation. [ABSTRACT FROM AUTHOR]